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 > Help! Onan 4K generator refuses to start and stay on

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bobndot

USA

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Posted: 01/15/21 05:05pm Link  |  Print  |  Notify Moderator

Blue smoke could be an overfilled oil res.

I copied the following from another rv tech post onan 4000

The carb on 4KY has a seal washer on INSIDE of float bowl, where fuel solenoid fitting comes through hole in bottom of bowl. If you have bowl off carb., and are not careful, or don't know this washer is there, it is easy to lose it.Then carb will not work correctly, will overfuel, etc. Might be something to check out. (been Onan tech 20+ years)

Another problem could be the fuel pump.

* This post was edited 01/15/21 05:14pm by bobndot *

pconroy328

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Posted: 01/15/21 09:09pm Link  |  Print  |  Notify Moderator

Kennyg wrote:

Pulled RV out of 6 month storage.


I suspect I know the answer, but -- did you run the generator, under load, for 45-60 minutes every month??? Like the manual says? [emoticon]

If not, then I'll also vote for a carb problem.

A new carb at an Onan dealer will run you $750. I know this from personal experience. Others have had some success by seafoaming, stabil-izing the snot out of the carb.

Maybe 70% of the problems I've followed over the years were carb. The second most popular were fuel pump for the Onan 4K.

Kennyg

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Posted: 01/16/21 10:08am Link  |  Print  |  Notify Moderator

Well, thanks for all of the advise. Will try all of the suggestions in next few days. Need to watch the packers first!!


Kennyg

whemme

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Posted: 01/16/21 04:11pm Link  |  Print  |  Notify Moderator

My vote is that you have a weak/inoperative electric fuel pump on your Onan generator


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ron.dittmer

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Posted: 01/17/21 07:08am Link  |  Print  |  Notify Moderator

whemme wrote:

My vote is that you have a weak/inoperative electric fuel pump on your Onan generator
I lean towards this too.

So many people go right to the carburetor when there is a problem. There are countless replies over the past 14 years I have been hanging out on RV forums, people saying "It's Your Carb", "Use Seafoam", Replace Your Carb".

For the past 32 years, I have been living in a house on an acre so I have a 18hp lawn tractor, 8hp roto-tiller, 8hp snow blower, and a 5hp power-washer, all of which are 4 cycle engines with simple carburetors. The tractor, tiller and snow blower are 32 years old. When I am done with any such equipment for the season, I simply place them aside. I don't do any storage preparation what-so-ever including never adding a fuel stabilizer. When I pull them out to use them as needed, I check the oil level or change the engine oil if it's time, and clean or change the air filter. I top off the fuel tank and they initially start rough, but after a minute, they smooth out and are ready to get work done. For the past 14 years, I have always applied the same practice to our Onan, yielding the same good results as my yard equipment.

Due to becoming "involved" grand parents along with world travel, this past summer marked a two year period since I previously started our motor home or our Onan. Two years was the longest duration yet so I was a tad bit concerned. The motorhome is stored indoors so I was fairly confident all would be well and I was right. The Ford V10 engine started instantly and smoothly as if I had it running an hour earlier. With a lot of priming in advance, the Onan started up fairly quickly, and behaved as it always did, requiring a minute or so to smooth out.

This past summer during that awakening, after 20 minutes of running properly under load running the a/c unit, my Onan suddenly shut off. After some research, I narrowed the problem down to the fuel pump. It became sensitive to working when it is very hot outside. When the day cooled off, the fuel pump worked fine. I have a new fuel pump and filter ready to install prior to our next trip.

I think much of the reason why Onan recommends running the generator once a month is because some are stored outdoors in very high humid environments. Running it as recommended might be for the sake of the power generating portion of the unit, not the engine itself.

As far as a "gummed-up" carburetor is concerned. Today's fuels are formulated to avoid that varnish that we dealt with in the days with carbureted automobiles. Vehicles today with high pressure fuel injection systems cannot tolerate "varnish" and such, so the fuel is so much cleaner than years ago. This "clean" fuel benefits small engine carburetors. There is no varnish build-up. There could be dirt build-up from a leaking air filter, so carb cleaners like Seafoam does have it's use. 2-cycle engines with oil in the fuel benefit greatly from carburetor cleaner products.

In many parts of the USA, fuels include a certain amount of alcohol. That cleans things better yet leaving even less residue in the carb as it evaporates away during the storage period, but the additive is hard on rubber gaskets and seals and such in many carburetors. It tends to dry them out, stiffening them, and in a worst case scenario, it cracks the rubber seals. My 1983 Toyota pickup truck I owned for 24 years, had a diaphragm in the side of the carb that the alcohol would dry up to the point that it no longer would move as it was supposed to. I had to change that part every-other year because of the alcohol in the fuel. Around these parts, I cannot buy gas without some amount of alcohol.


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wopachop

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Posted: 01/17/21 08:31am Link  |  Print  |  Notify Moderator

Does your float bowl have a drain on the bottom?

Dutch_12078

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Posted: 01/17/21 08:35am Link  |  Print  |  Notify Moderator

Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...


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Kennyg

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Posted: 01/17/21 08:42am Link  |  Print  |  Notify Moderator

wopachop wrote:

Does your float bowl have a drain on the bottom?

YES - Have drained it number of times and very little comes out. Finally, I have pulled gas line and hit start button and definate volume of gas is being seny to input of bowl .

Can someone explain the purpose of the solenoid on carb?

Kennyg

Green bay, Wi 54303

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Posted: 01/17/21 08:49am Link  |  Print  |  Notify Moderator

Dutch_12078 wrote:

Does the generator keep running if you hold down the start switch? If it does, that indicates that it's not putting out enough voltage to the control board to lock in the run cycle. It could be a faulty voltage regulator ($$$), or it could be dirty slip rings. Holding the start button down for a minute or two may clean the rings enough to keep it running. Worth a try anyway...


No. will run ,but as soon as I release button, the engine stops.

bobndot

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Posted: 01/17/21 10:59am Link  |  Print  |  Notify Moderator

https://www.irv2.com/forums/f54/onan-gas........nerator-fuel-cutoff-solenoid-456887.html

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